This study develops a quantitative kinetic framework for graft copolymerization of methyl methacrylate (MMA) and styrene (ST) onto natural rubber latex (NRL), with emphasis on Redox initiation and Interfacial polymerization in a multiphase system. Experiments were conducted using a cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA) system. Core–shell particles, consisting of a soft NR core and a rigid poly(vinyl monomer) shell, were obtained at 40–60 °C with initiator concentrations of 0.0051–0.0205 mol L−1 and monomer concentrations of 0.39–0.83 mol L−1. Radical generation occurs predominantly at the aqueous rubber interface, where monomer partitioning takes place between phases. This leads to simultaneous homopolymerization in the aqueous phase, while grafting occurs on the rubber backbone. Overall conversion (xp), graft conversion (xg), and grafting efficiency were determined gravimetrically, while morphology was confirmed by FTIR and TEM. The conversion profiles show nonlinear behavior consistent with power-law kinetics, allowing formulation of rate expressions for overall polymerization rate (Rp) and grafting rate (Rg). Reaction order and Arrhenius analyses indicate fractional, heterogeneous behavior characteristic of multiphase reaction kinetics. Styrene shows lower activation energy, whereas MMA exhibits higher collision frequency. The model reproduces experimental trends well (R2 up to 0.95) and provides insight into propagation–grafting competition in natural rubber latex systems.
Arayapranee et al. (Wed,) studied this question.